Many machine tools, particularly modern machining centers, have a main spindle with a bore adapted to receive a variety of tools, each having a commonly configured tool shank. One frequently encountered tool is a complex head which has the commonly configured tool shank at one end, and which may be stored in a tool storage matrix on machines having automatic tool changing mechanisms. This complex head is often referred to as a boring and facing head, where the other end of the head supports a tool bar, for example, a single point turning or boring bar. The tool bar needs a variable swing, and is thus required to be adjustable in a direction transverse to the spindle and tool shank axis. This transverse direction is known as the "U-axis" of a machining center. The main body of the head includes a slideway, transverse to the central axis, and an interior mechanism for the transverse adjustment, where the interior mechanism might, for example, comprise a rotatable lead screw engaging a nut affixed to the transverse tool slide carrying the tool bar. The boring and facing head main body has a radially extending arm which includes a drive train, and which, at its outermost end, supports a drive shaft extending parallel to, and in the same direction as, the tool shank. The outer end of the drive shaft has a rotary coupling element which mates with a motorized tool member rotation device on the machine tool. The tool member rotation device is driven by a servomotor which may precisely rotate the drive shaft and, consequently, accurately position the tool bar along the U-axis. This precise movement may occur while the main spindle of the machine and the tool shank are either rotating or stationary.
Two patents are instructive as to how prior art boring and facing heads may be constructed; they are, U.S. Pat. Nos. 4,489,629 of D'Andrea et al, Dec. 25, 1984, and 4,607,549, of Krempel, Aug. 26, 1986. Each of these patents shows a wedge-shaped blade or tang as part of an input drive shaft, where the tang is to be received in a complementary mating socket on the machine tool, when the tool shank of the head is received with the machine spindle and retained by well-known drawbar retention means. The configuration of the torque couple for transmitting rotary motion to the drive shaft is relatively unimportant. Many variations are possible, e.g., an inversion where the drive tang is located on the machine tool servo motor and the input drive shaft of the boring and facing head has a complementary mating socket.
The head patents do not address a method or an apparatus for keeping the tool connecting portion of the tool member rotation device free of chips, coolant, and other contaminants which may find their way into the exposed mechanism when the boring and facing head is not present on the machine.
It is known in machine tool arts to provide a blast of compressed air to a machine tool element to clear a tool shank socket of chips and contaminants; such a system is shown in U.S. Pat. No. 4,404,728, of Ishikawa, Sep. 20, 1983.
Another system for maintaining cleanliness in a tool receiving and registration mechanism is found in U.S. Pat. No. 3,512,817, of Attermeyer, May 19, 1970, in which a machine station and detachable workpiece pallet are each fitted with a precision multi-tooth facial coupling half, and each half is covered by a thick rubber membrane seal. The seal is deflected away from the facial teeth of a coupling half by a projecting rim on the mating half which leads the way as the coupling halves are joined with one another. When the joint is later broken, and the coupling halves are separated, the deflected rubber membrane seals will return to their normally biased positions covering the facial teeth.
Several drawbacks are presented by these prior art methods for sealing and maintaining cleanliness of tool registration surfaces: in the purging system, a blast of air or other fluid may be insufficient to exclude or remove large chips of metal, which frequently have burrs and tend to snag; and, the deformable membrane seal device requires custom molded elements, which are very expensive and tend to fatigue in use and thereby lose bias resiliency, or shape memory. The present invention overcomes these problems inherent in the prior art.